Bomb



E. l. LINDMAN Aug. 19, 1952 BOMB Filed June 11, 1945 %N NM \m QM W J IrvH Fatented Aug. 19, 1952 OFFICE BOMB Emrik Ivar Lindman, Ronningm'swedenApplication June 11, 1945, Serial No. 598,857 In Sweden October 7, 1940Section 1, Public Law 690, August 8, 1946 Patent expires October 7, 1960Dummy or practice bombs to be thrown from airplanes are often made ofconcrete. It has been proposed to weight such bombs with pieces of wasteor'scrap iron introduced into the concrete in order to give the bomb asufiicient weight. This also renders it possible to' adjust the positionof the centre of gravity to a certain extent. Among other features, theweight of the bomb and theposition of its centre of gravity have apreponderant influence upon the ballistic qualities of the bomb.

These bombs, however, are rather unsatisfactory and they'have not thesame ballistic qualities as real fighting or explosive bombs. Conse-.quently, these dummy bombs are not suitable for an efiicient training ofthe air-men. In addition, practice bombs heretofore known have veryvariable ballistic characteristics, though every effort was made attheir manufacture to get a uniform product. Consequently, the pattern orspread is bad when such bombs are thrown. One cause of this drawback isthat the pieces of scrap iron in the concrete are easily displacedduring the solidification of the concrete, thus essentially changing theballistic characteristics of the practice bomb.

The chief purpose of this invention is to create a practice orindicating bomb which has good, constant and uniform ballisticcharacteristics but nevertheless is simple and inexpensive tomanufacture. In accordance with the invention bombs may be producedwhich have the prescribed, predetermined ballistic characteristicswithin very narrow limits, and consequently may be dropped with aminimum of spread, that is with a good pattern. Consequently, thebombing practice may be carried out with the same accuracy asthatattained in throwing real fighting bombs, and such practice is far morevaluable than the ordinary practice heretofore possible.

It is a well-known matter of fact that fighting bombs of steel aremanufactured with very high precision in those ballistic features whichare decisive for the path of the bomb through the air. Thus, it ispossible to throw such bombs with high accuracy on the target. however,heretofore not be attained, when manufacturing and using practice bombsof concrete. Certainly, efforts were made to give the concrete bomb thesame external shape as the corresponding steel bomb, as accurately aspossible, but in spite of this the concrete bombs differ very much inother ballistics data from the steel bombs, and

also are very variable in such ballistic data. For instance, it was notpossible to attain a cor- This could,

1 Claim. ('Cl. 102--7.6)'

, 2 reel; position of the centre of gravity and simultaneously a correcttotal weight of the bomb, within reasonably narrow limits.

Consequently such practice bombs of concrete were unsatisfactory and notsuitable for an efiicient training of the air-men. The pattern or spreadis bad, when such bombs are thrown. For these reasons, the militarysupplies authorities found it impossible to prescribe any weight limits,but had to be content with demanding a certain accuracy in the externalshape of the bomb. As a matter of fact it was heretofore impossible toattain the desired accuracy in external shape, total weight and positionof the centre of gravity. It does not suffice to use exactly the samemould and to pour concrete in it, because even if the components of theconcrete are weighed and mixed with high accuracy the composition of theconcrete varies much, and consequently concrete bombs moulded in thesame mould turn out to be very different. It must be observed thatconcrete absorbs water, also after it has dried. The decisive ballasticdata, such as the position of the center of gravity, the total weightand the external shape, are predetermined with regard tothe desiredballistic properties of the steel bomb, taking the properties of thesteel into consideration, and it was heretofore impossible to attain thesame data in concrete bombs, concrete having quite different properties.To render concrete bombs really valuable for practice purposes, smallbombs should be so accurate that, for instance, their total weightdiffers at most i1%from the prescribed average value for thecorresponding sharp or fighting bomb of steel. For very big bombs, thistolerated limit may be increased to il Hereto-fore, it was absolutelyimpossible to attain values even in the neighbourhood thereof; evensteel bombs could not always be manufactured with sohigh accuracy.

In accordance with my invention, the air bombs may be made of partswithdifferent specific gravity or different weight'per unit of volume, whichare solidified, dried and weighed. Then such parts are united whichtogether give the desired total weight and also the correct position ofthe centre of gravity of the bomb. Thus, the whole bomb may bemanufactured with'the very high accuracy demanded, though it is notpossible to manufacture the parts separately with such accuracy The veryfact that a body of concrete cannot be moulded (cast) with apredetermined high acouracy led to the idea that it was impossible tomanufacture concrete bombs 3 with high accuracy in respect of theirweight. It should perhaps be mentioned that such accuracy cannot beattained by weighing a predetermined quantity of concrete mass and thenintroducing said weighed quantity into the same mould. It will be foundthat nevertheless the finished concrete bombs thus producedvaryjextensively in their total weight.

The low price and high accuracy of the bombs in accordance with theinvention renders it advantageous to use them for practice purposes for1.1 sighting-shots and other indicating, purposes.

Embodiments of bombs in accordance with this invention are shown in theannexed drawing, c

Fig. 1 shows a longitudinal section through. a. 1-5: (big) bomb inaccordance with the invention.

Figs. 2 and 3 show cross sections on thei'lines IIII and IIIIII,respectively, in Fig. 1.

Fig. 4 is a longitudinal section through .a (small) bomb in accordancewith a modified embodiment.

Referring now to Figs. 1.3 of the drawings, a central tube 2,for-instance of meta-1,,extends through the wholelength of the bomb and,preferably, projects beyond its rear; part or tail. In

the embodiment shown Said, tube has a constant cross section, but the.cross sec i n y a be varied, preferably in such manner that the tube 2.has'a larger cross section towards the tail of the bomb. Around the tube2 the body properof the bombis mouldedofconcrete. In the embodimentshown, the, concrete. body is made of two parts. ,I and 3 but in certaincases; it may be suitable to. make the concrete, body of another num--ber of parts.

The concrete is, composed; of a; binder, preferably; of the hydraulictype, such as cement, togetherwith different mixtures of heavy sand,thaliis sand having; a higher specific gravity. than. 3.0;. In certaincases binders Of. the asphal- 40 tic-type or. of other types may beused, Th heavy sand, may consist of ore concentrate or of fine grainzoripreferablyrirongore.1 To it s n of:;ordi-nary.granite, gneiss or-thelike, or of concrete. clinkenpumice or the like. may: be admixed Toattain a high wei ht p r un o lume o the concret th sand: may be. mix wih o entirely. cons st; o g anulated; ir n o. all d ranule manufactured bla n p iron in water) or lead, The word sand here has the sense acceptedintheconcrete technics and; consequently indicates particles. up to? mm.By proportioning the'difierent types of sand in relation to each otherandto. the bindenit isconsequently possible to control the weight perunit of volume to any desiredvalue, within the limits herein concerned.a

Preferably, the bomb is cast inravertical mould,

, and concrete with the desired weight per unit of; volume is poured ondifferent levels, after the preceding pouring has solidified. Thus, itis possible to cause the centre of gravity to assume the desiredposition, while simultaneously the total weight of the bomb gets thedesired value. First the part I is cast which hasthe dominatinginfluence upon the total weight. After this part has. solidified, it isweighed, and connected with the part 3. The part 3 may be poureddirectly upon the part I already solidified or the part 3 may. first bemoulded separately and then se- 7 cured in its plane on the bomb, forinstance, by means of cement mortar inserted between the parts I and 3and between the part 3.. and the tube 2. If the part 3'is cast directlyonthe part I the quantity of concrete for thepart. 3..is. first weighedso that it renders the prescribed total weight of the bomb together withthe part I (after the weight of such metal parts have been deductedwhich possibly were not weighed together with the part I). If the part 3is manufactured separately, series of such parts are generallymanufactured, which are weighed after the solidification and then arecombined with such parts I as will give the desired total weight. It hasbeen found that when bombs are manufactured on a large scale suchadjustment of the weight may be made at a low cost.

In one preferred embodiment for small bombs, the nose of; the bomb ismade of cement, iron ore concentrate and granulated iron in theproportions 1:3:3. About 20-30% of the total weight .of the bomb is madeof such concrete.

The remainder of the part I, that is about -70% by weight of 'the totalweight, is made of concrete consisting only of cement and concentrate ofironore in the proportions; 1:3. Finally, the part 3 is made of concretehaving a lower specificrav ty- It, is very important that the concreteof everybomb has a homogeneous composition and receives the sametreatment. It has been found that the best results are obtained byvibrating the concrete at a-hi-gh frequency, for instance, in a machinegenerating the vibrations as elastic oscillations in the material of thevibratingma,-- chine proper.

When the tube 2 is inserted into the concrete, it is well anchoredtherein due to the shrinking of the concrete. If desired, specialmeasures, may be taken for anchoring; the tube 2 in the concrete.

The bomb shown in Figs. 1-3 isv intended to behung horizontally in theairplane. For this purpose irons t, 5 are laid in the-concrete and bentaround thecentral tube, as shown in Fig. 2. The forward iron 4 is bentin a direction opposite to that of the. rear iron 5; sothat the bomb hasasymmetrical distribution of the weight in relation to. its longitudinalaxis or a longitudinal plane. In those ends of the irons 4, 5whiehextend to the surface of the bomb threaded holes. 6 ar made foreyes or hooks in which the bomb is hung.

In; this embodiment the bomb has tail vanes; I stayed by an iron ring 8.The vanes have a metal cone 9 enclosingtherear part of thebomb.

In the tube 2 a suitable indicator charge is; arranged, such as a smokeforming charge or" a. light emitting charge or both. For igniting; this;charge, either by direct shockaction or by means, of an igniting charge-(primer or fuse) and/or anexpelling charge (detonator) a firing pin I0is arranged in the forward portion of the tube 2. This pin. is securedtoa plate II which upon impactagainst the ground drives the pin II)inwards; and thus ignites the indicator charge. A safety cap I2 may beprovided to protect: the pin during transportation. I

The parts I and 3 are often made of concrete having diiferent Weightsper unit of volume. It has turned out that the slight change of theyposition of the centre of gravity which is. due to the fact that parts.3- of somewhat different weights are used, generally may be neglectedwithout inconvenience. In such cases, in which the allowable limits ofthe position of the centre of gravity are too small to permit av part 3to be secured to the tail of the bomb, the final ad-- justment of thetotal weight is made, in arecess in the part Ia adjacent to the, centreof gravityof the bomb, as shown in Fig. 4. In such cases only theforward or nose portion of the tube 2 is cast into the concrete, whilethe tail part of said tube is surrounded by a free channel 3I producedby inserting a second tube from the rear end (from the top of the mould)into the mould around the tube 2. This second tube is removed, as soonas the concrete has solidified. After the part Ia thus produced has beenweighed to find its exact weight, a fixed amount of concrete 30 isintroduced through said channel 3I towards the nose of the bomb, that istowards the centre of gravity, and this addition is left to solidify.The rear end of the channel around the tube 2 may then be sealed in anysuitable manner, as shown at 32.

Also in Fig. 4 the practice or indicator bomb I is made of concrete withsuch additions (such sand) that the bomb gets substantially the sameballistic characteristics as a fighting bomb of the same size. The bombhas tail vanes I. The tube 2 has a shoulder or abutment which in theembodiment shown consists of a screw I! screwed through the wall of thetube. From the nose of the bomb a tube I8 is pushed into the tube 2. Therear end of the tube I8 abuts against the screw I1 and the tube I8 isfilled with an explosive, preferably black powder, though in some casesnitrous powder may also be used. In the upper or nose end of the tube I8a primer I9 is arranged.

The striking plate I I has an eye 20 for hanging the bomb vertically inthe airplane.

The plate I I is normally locked by a safety device 33, which is removedwhen the bomb is thrown from the airplane in well-known manner.

Below (behind) the powder-filled tube I8 a tube 21 is placed which, forinstance, contains a smoke-forming substance or a light-emitting charge,which is expelled (or ignited and expelled) by the explosive in the tubeI8 when the bomb strikes the ground. The tube 21 is secured by means ofa split pin 28, a resilient hook or the like.

Because the weight of a body of concrete varies with its percentage ofhumidity, it is suitable to coat the finished bombs with a non-adhesive,water-repulsing coating, such as paramn wax. It is suitable to use asolution of solid paramn in a liquid hydrocarbon, such as benzene, whichevaporates after the coating process. Bombs thus coated have a constantweight even if they are stored or subject d to rain or the like.

6 It has turned out that bombs in accordance with this invention may bemanufactured with the same accuracy as fighting bombs, as far as theballistic characteristics are concerned. Consequently the practice orindicator bombs in accordance with this invention may be dropped with atleast the same accuracy as fighting bombs in spite of the fact that thecost of manufacture of the bombs in accordance with this invention isonly a small fraction of the costs of corresponding fighting bombs. Anaccuracy of i1% in the total weight and other ballistic elements mayeasily be attained by use of this invention.

Some of the features illustrated and described herein are alsoillustrated and described but not claimed in my copending U. S. patentapplications Serial No. 417,728, filed November 11, 1941, now Patent No.2,456,289 and No. 598,856, now abandoned, filed simultaneously with mypresent application.

What I claim is:

A method of manufacturing air bombs for practice and other purposes,comprising, casting the body of the bomb around a central tube in avertical mould, while leaving a channel around said tube in the rearpart of the bomb, weighing said body with its tube after the concretehas assumed its permanent solidified state, and casting a predeterminedquantity by weight of concrete into said channel to render the desiredtotal weight and the desired center of gravity of the bomb.

EMRIK IVAR LINDMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain Feb. 17, 1939

